Ash cloud Fishyness

Thursday 15th april 2010 and a volcanic ash cloud from iceland has grounded all flights in and out of the uk and much of western europe. The uks
aviation authority Nats has said its unsafe to fly in and out of the ash cloud because of fears that it could damage the planes jet engines.

All the while the airlines are crying out to be allowed to fly, british airways cheif executive takes to the skys to test the effects of ash on the
jet engines, and big surprise, there is no effect.
After this revealing a couple of days later british airspace was once again opened, and flights returned to normal, until today.

Tuesday 4th may 2010 and its now been deemed that its unsafe to fly in ireland and in some parts of scotland again as a new ash cloud has drifted
southwards towards us. But i thought we already discovered that we can fly through the ash and it has no effect on the engines.
Is it just me who thinks this whole, we can fly, we cant fly, we can, we cant attitude smells a bit fishy. i mean if i didnt want someone flying what
better way to do it than to make people think it was for their benefit.

It's for safety issues. The rather large sediements and dust in volcanic ash clouds have been proven to make Jet engines stall, infact I've heard of
an incident where a pilot made the decision to fly straight through an oncoming ash cloud, next thing they know, their engines have failed, and they
are now gliding through the sky, took a whole 20 minutes to start back up again apparently. I can't remember when this happen, but I know it was a
few years ago.

Anyway, it's basically just for passenger and crew safety, I'm pretty sure the tourism industry doesn't want any un-necessary blood on their
hands.

reply to post by Damezthe2ndThat was the first thing i thought of
when the ash in the sky first came to light. I think the powers that be said it was unprecidated to have uk airspace closed. But obviously the
volcano must have happened so i dont know about a terror threat, however if it is true that volcanos and earthquakes are happening all the time all
over the earth, why havnt i heard of airspace being closed more regularly, maybe i dont read the papers enough!

damned if they do and damned if they don,t get a grip folks it was a safety issue.
if a plane had come down every one would have been screaming , why the hell did they let the planes fly when there was a possibility of danger .

It is important to make a distinction between flight through (or in the immediate vicinity of) an eruption plume, and flight through the so-called
affected airspace. Volcanic ash in the immediate vicinity of the eruption plume is of an entirely different particle size range and density to that
found in downwind dispersal clouds, which contain only the finest grade of ash. The actual level of ash loading which catastrophically affects normal
engine operation has not yet been established, beyond the knowledge that relatively high ash densities must exist for this to happen. Whether this
silica-melt risk still remains at the much lower ash densities characteristic of downstream ash clouds is currently unclear. This is however a serious
safety hazard which requires preventive risk-management strategies, in line with other comparable aviation hazards.

Volcanic ash particles have a maximum residence time in the troposphere of a few weeks. The finest tephra particles remain in the stratosphere for
only a few months

So it would seem that the heavier/denser material in the plume remains in the troposphere which extends up to around 33,000 feet, from which it
normally falls back to earth within a few weeks. The lighter material can stay up in the stratosphere for months.

The stratosphere extends from around 33,000 feet above sea level to approximately 164,000
feet.
Commercial airlines typically operate between 31,000 and 37,000 feet.
Most of them are certified to operate at ceilings up to around 42,000 feet.

If this is a ruse, then it's a particularly convenient one because it's extremely difficult for Joe Public to directly ascertain the quality of the
air in these stratified layers more than 30,000 feet above our heads (anyone got a spare weather balloon in their garden shed?).

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